Field of the Invention
This invention relates generally to window structures for buildings, vehicles or other applications and, more particularly, to a window capable of controlled failure from blast pressures due to explosions, bomb blasts, car bombs, and the like.
Technical Considerations
Terrorist attacks utilizing explosives, such as grenades, bombs, or similar devices, are increasing in an ever more dangerous world. One of the weakest points on a structure, such as a building or vehicle, is the window or similar transparent glass area. In the event of an explosion outside of the building, people in the building can become injured as the result of shattered and flying glass fragments entering the building. A conventional response to this threat is to make the window stronger and more resistant to blast damage. This can take the form of using glass panes of increased thickness, using laminated glass structures, applying safety films or sheets to the glass, or incorporating perforated metal sheets into the window structure to help prevent blast damage. However, as a general rule, the more components added to the window to increase the window strength, the lower the visible light transmittance of the window and the harder it is to see through the window. Also, conventional precautions, such as perforated metal sheets or other metallic structures, can be easily seen. This would alert a potential attacker that the window is a blast-resistant window.
In some applications, it would be advantageous to provide a window with a controlled failure orientation such that, in the event of an explosive blast exterior to the building, the window would break in a pre-selected orientation and/or remain connected to the window frame to reduce damage or injury to the building occupants. It would also be advantageous if such a failure oriented window were not easily detectable by viewing with the naked eye so that potential attackers would not know that the window is a safety window.